Some magnetic random access memories (MRAM) have a configuration in which a magnetic tunnel junction (MTJ) element exhibiting the tunneling magnetoresistive (TMR) effect is used for a data memory unit. The configuration is drawing attention as a high-speed and large-capacity nonvolatile memory. Writing to the memory layer of the MTJ element is performed by, for example, a spin-transfer torque writing system. In the system, for example, a current is passed directly through the MTJ element and a spin-transfer torque injected from the reference layer of the MTJ element is used to reverse the magnetization of the memory layer. It is important to ensure stable operation in such a magnetic memory element.